A
bstract
We update predictions for lepton fluxes from the hadroproduction of charm quarks in the scattering of primary cosmic rays with the Earth’s atmosphere. The calculation of charm-pair ...hadroproduction applies the latest results from perturbative QCD through next-to-next-to-leading order and modern parton distributions, together with estimates on various sources of uncertainties. Our predictions for the lepton fluxes turn out to be compatible, within the uncertainty band, with recent results in the literature. However, by taking into account contributions neglected in previous works, our total uncertainties are much larger. The predictions are crucial for the interpretation of results from neutrino experiments like IceCube, when disentangling signals of neutrinos of astrophysical origin from the atmospheric background.
A
bstract
We present predictions for the prompt-neutrino flux arising from the decay of charmed mesons and baryons produced by the interactions of high-energy cosmic rays in the Earth’s atmosphere, ...making use of a QCD approach on the basis of the general-mass variable-flavor-number scheme for the description of charm hadroproduction at NLO, complemented by a consistent set of fragmentation functions. We compare the theoretical results to those already obtained by our and other groups with different theoretical approaches. We provide comparisons with the experimental results obtained by the IceCube Collaboration in two different analyses and we discuss the implications for parton distribution functions.
A
bstract
The impact of measurements of heavy-flavour production in deep inelastic
ep
scattering and in
pp
collisions on parton distribution functions is studied in a QCD analysis at next-to-leading ...order. Recent combined results of inclusive and heavy-flavour produc- tion cross sections in deep inelastic scattering at HERA are investigated together with heavy-flavour production measurements at the LHC. Differential cross sections of charm- and beauty-hadron production measured by the LHCb collaboration at the centre-of-mass energies of 5, 7 and 13 TeV as well as the recent measurements of the ALICE experiment at the centre-of-mass energies of 5 and 7 TeV are explored. These data impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions
x
of the proton momentum, down to
x ≈
10
−
6
. The impact of the resulting parton distribution function in the predictions for the prompt atmospheric-neutrino fluxes is studied.
Abstract
Cosmic rays (CRs) govern the energetics of present-day galaxies and might have also played a pivotal role during the Epoch of Reionization. In particular, energy deposition by low-energy (E ...≲ 10 MeV) CRs, accelerated by the first supernovae, might have heated and ionized the neutral intergalactic medium (IGM) well before (z ≈ 20) it was reionized, significantly adding to the similar effect by X-rays or dark matter annihilations. Using a simple, but physically motivated reionization model, and a thorough implementation of CR energy losses, we show that CRs contribute negligibly to IGM ionization, but heat it substantially, raising its temperature by ΔT = 10–200 K by z = 10, depending on the CR injection spectrum. Whether this IGM pre-heating is uniform or clustered around the first galaxies depends on CR diffusion, which, in turn, is governed by the efficiency of self-confinement due to plasma streaming instabilities that we discuss in detail. This aspect is crucial to interpret future H i 21-cm observations, which can be used to gain unique information on the strength and structure of early intergalactic magnetic fields, and the efficiency of CR acceleration by the first supernovae.
A
bstract
Effects on atmospheric prompt neutrino fluxes of present uncertainties affecting the nucleon composition are studied by using the PROSA fit to parton distribution functions (PDFs). The ...PROSA fit extends the precision of the PDFs to low
x
, which is the kinematic region of relevance for high-energy neutrino production, by taking into account LHCb data on charm and bottom hadroproduction collected at the center-of-mass energy of
s
=
7
TeV. In the range of neutrino energies explored by present Very Large Volume Neutrino Telescopes, it is found that PDF uncertainties are far smaller with respect to those due to renormalization and factorization scale variation and to assumptions on the cosmic ray composition, which at present dominate and limit our knowledge of prompt neutrino fluxes. A discussion is presented on how these uncertainties affect the expected number of atmospheric prompt neutrino events in the analysis of high-energy events characterized by interaction vertices fully contained within the instrumented volume of the detector, performed by the IceCube collaboration.
We use the crpropa code to simulate the propagation of ultrahigh energy cosmic rays (with energy ≥1018eV and pure proton composition) through extragalactic magnetic fields that have been simulated ...with the cosmological enzo code. We test both primordial and astrophysical magnetogenesis scenarios in order to investigate the impact of different magnetic field strengths in clusters, filaments and voids on the deflection of cosmic rays propagating across cosmological distances. We also study the effect of different source distributions of cosmic rays around simulated Milky Way-like observers. Our analysis shows that the arrival spectra and anisotropy of events are rather insensitive to the distribution of extragalactic magnetic fields, while they are more affected by the clustering of sources within an ∼50 Mpc distance to observers. Finally, we find that in order to reproduce the observed degree of isotropy of cosmic rays at ∼EeV energies, the average magnetic fields in cosmic voids must be ∼ 0.1 nG, providing limits on the strength of primordial seed fields.
We constrain the energy at which the transition from Galactic to extragalactic cosmic rays occurs by computing the anisotropy at Earth of cosmic rays emitted by Galactic sources. Since the diffusion ...approximation starts to loose its validity for E/Z > ~ 10 super(16-17) cV, we propagate individual cosmic rays using Galactic magnetic field models and taking into account both their regular and turbulent components. The turbulent field is generated on a nested grid which allows spatial resolution down to fractions of a parsec. Assuming sufficiently frequent Galactic CR sources, the dipole amplitude computed for a mostly light or intermediate primary composition exceeds the dipole bounds measured by the Auger collaboration around E asymptotically = 10 super(18) cV. Therefore, a transition at the ankle or above would require a heavy composition or a rather extreme Galactic magnetic field with strength > ~ 10 mu G. Moreover, the fast rising proton contribution suggested by KASCADE- Grande data between 10 super(17) cV and 10 super(18) cV should be of extragalactic origin. In ease heavy nuclei dominate the flux at E > ~ 10 super(18) cV, the transition energy can be close to the ankle, if Galactic CRs are produced by sufficiently frequent transients as e.g. magnetars.
► Ultrahigh energy heavy nuclei deflected in the Galactic magnetic field. ► Both regular and turbulent Galactic magnetic field components are modeled. ► Turbulent field impact on source images at low ...and high Galactic latitudes. ► Strong source fluxes (de)magnifications reduced by the turbulent field. ► Cen A cannot be the sole source of all UHECR detected at Earth above 55
EeV.
In this work we study how the turbulent component of the Galactic magnetic field (GMF) affects the propagation of ultrahigh energy heavy nuclei. We investigate first how the images of individual sources and of the supergalactic plane depend on the properties of the turbulent GMF. Then we present a quantitative study of the impact of the turbulent field on (de-)magnification of source fluxes, due to magnetic lensing effects. We also show that it is impossible to explain the Pierre Auger data assuming that all ultrahigh energy nuclei are coming from Cen A, even in the most favorable case of a strong, extended turbulent field in the Galactic halo.
The majority of the matter in the universe is still unidentified and under investigation by both direct and indirect means. Many experiments searching for the recoil of dark-matter particles off ...target nuclei in underground laboratories have established increasingly strong constraints on the mass and scattering cross sections of weakly interacting particles, and some have even seen hints at a possible signal. Other experiments search for a possible mixing of photons with light scalar or pseudo-scalar particles that could also constitute dark matter. Furthermore, annihilation or decay of dark matter can contribute to charged cosmic rays, photons at all energies, and neutrinos. Many existing and future ground-based and satellite experiments are sensitive to such signals. Finally, data from the Large Hadron Collider at CERN are scrutinized for missing energy as a signature of new weakly interacting particles that may be related to dark matter. In this review article we summarize the status of the field with an emphasis on the complementarity between direct detection in dedicated laboratory experiments, indirect detection in the cosmic radiation, and searches at particle accelerators.
Based on new developments in the understanding of supernovae as gravitational-wave (GW) sources, we estimate the GW background from all cosmic supernovae. While our estimate is uncertain within a few ...orders of magnitude, this background may become detectable by second-generation space-based interferometers such as the proposed Big-Bang Observatory. At frequencies below about 1 Hz this GW background is stochastic. Down to about 0.01 Hz it could well be of comparable magnitude to the one expected from standard inflationary models, especially in the presence of an early population of massive stars.
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